Reversible circulation internal fan kiln



May"26,` T925. 1,539,81 7

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed April 19, 1924 2 Sheets-Sheet l INVENTOR P l HELEN mA/V Mhz/HLW* \YO000O0OO 0000000 0000000000 0000 b Z OO E/.xoooooo oooao oooo 5 ,w K/ A w m www? ` ATTORNEYS.

May 26, 1925. l 1,539,817

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed April 19, -1924 2 Sheets-Sheet 2 .Y INVENTOR. 'Figs-2 @LF IHELEN AMA/#MMM BY Lw..

A T'I'ORNEYS,

Patented May 26, 1925.

UNITED STATES .PATENT OFFICE.

ROLF THELEN, orv

THE PEOPLE 0F THE UNITED STATES.

REVERSIBLE CIRCltll'ItAlION` INTERNAL FAN KILN.

Application led April 19, 1924. Serial No. 708,323.

(GRANTED UNDER THE ACTl 0F MARCH 3, 1883; 22 STAT. 11.825.)

To all who-m it may concern.' i Be it known that I, ROLF THELEN, a citizen of the United States of America, and an employee-of the Department of Agriculture, residing in Madison, Wisconsin (whose Apost-ofice address is Forest Products Laboratory, Madison, Wisconsin) have invented a new and Improved' Reversible Circulation Internal Fan Kiln.

This application is made under the act ot March 3, 1883, chapter '143 (22 Stat. 625), and the invention herein described and claimed may be used by the Government of the United States, its officers and employees, and by any person inthe United States without the payment tome of any royalty thereon. Ihereby dedicate the same to the free use of the Government and the people of the United States.

My invention consists in an improvement in the design of forced circulation kilns or chambers for drying and conditioning lumber or similar material. However, its use is not limited to wood or wood products.- lIt consists in the adaptation of fans of the disk type, or similar types, to the production of a uniquelinternal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 3. Figure 1 represents a cross-sectional; elevation. Figure 2 represents a horizontal section taken at various elevations below the track level. Figure 3 represents a longitudinal sectional elevation of the fans and adiacent parts.'

. The principal 'feature which I claim asnovel and an improvement over existing kilns is the use and arrangement of the fans and the air distributing system. This arrangement is such that a very fast and uniform circulation of "air and vapor through the piles of .lumbenmay be' secured and it permits the lperiodic reversal o fl-the' direction -ot' the air movement by simply. reversing the direction of rotation'of'the fans. The air distributing systemV rofvdes a very uniform iiow of air throng V*out the length and breadth of the kiln andfel'Lmif nates the non-uniformity of drying, whichl is one of vthe commonest troubles experienced m the ordinary kiln. The arrangement of poses.

the specification describes certain specificmeans of producing a brisk circulation; and

the elimination t'of comparatively small ducts such as those used in external blower kilns reduces` very materially 'the work required tovproduce a given circulation. The

differences in air pressure required in -the operation of this kiln are much smaller than those ordinarily required in kilns em ploying centrifugal blowers, and the disk fans operate very eiiiciently at these low pressures. Measurements recently made indicate that the static pressures necessary for the successful operation of this system are materially less than oneheighth of an inch of water pressure. It is possible, therefore, by the use of this invention to produce a, very great and uniform circulation of air and vapor within the kiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the use of internat fans can be adapted to dry kilns of different types, this invention is limited to double track kilns in which the lumber is edge stacked. In edge stacked lumber the width of each board is in a vertical direction, the

thickness and length being in horizontal directions.

Any well-known means of heating thefair and the vapor in the kiln may be used in conjunction with this invention. When steam pipes are used they may be arranged beneath the lumber piles at the sides of the kiln or in any other convenient manner. Any convenient form and arrangement of heaters may be used.

The drawings show and the'specificat'ron describes steam jet pipes for increasing the humidity, and air inlet iues and air outletliues with suitable dempers for decreasing the humidity.

While the drawingsshow and the specitication' describes specific means for heating the air "and, thev vapor in the kiln and for regulating. the humidity gof vthe air in the kiln'. Athis invention isnot limited specifically jtq the arrangements described,l but may able means for accomplishing the Ysame -pur-l While the drawingsillustrate and forms of piling, the invention is not limited to these particular forms since it is equally applicable to other forms; neither is the invention. limited tothe specific form of rails, trucks, and track supports illustrated in the drawings and described inthe specificat'ion. y

Referring" to Figures l, 2, and 3, which are correspondingly lettered: AA represent the side deflecting partitions. These partitions serve to form a passageway for the air from the heating coils to the fans and vice versa. BB are the fans producing the circulation. Straight-bladed disk fans are preferable. Any type of fan, however, in which the reversal of the direction of rotation of the fan produces a reversal in the direction of the flow of the air current passing through the fan can be used. C is the shaft upon which the fans are mounted. Provision is made to take care of the expansion and contraction of this shaft with changes in the temperature in the kiln and to take care of v the thrust of the fans. This provision con- ,sists in equipping one of the bearings II with suitable thrust rings or collars and equipping all of the4 other bearings II with any wellknown means for longitudinal motion. Plain bearings and roller bearings require no special provision of this kind. Certain types of ball bearings require housings which permit the entire bearings to slide longitudinally within them. DD are air inlet dampers used to regulate and control the amount of air entering the kiln from the outside. EE are the heating coils. These may be of the return bend type or other convenient type. F is the steam jet pipe used to increase the humidity of the air in the kiln. Suitable openings are provided to permit the escape of the steam throughout the length of the kiln. Various other common and well-known arrangements may be used. GG are the lumber-supporting trucks. HH are the shaft hangers. II are bearings for the shaft C. JJ are the tracks upon which the lumber-supporting `trucks run. KK are the side walls of the kiln. LL is the lumber to be dried. MM are the track supports. N is the shaft pulley. OO are airoutlet dampers for controlling the amount of air being exhausted from the kiln. l? is a belt passing over the pulleys N and Q. Q is the motor pulley.A R is the motor which furnishes the power to drive the fans. S is the switch for controlling the speed and rotation of the motor armature. While the drawings show and the specification describes an electric motor, any other suitable drivin` means may be used. lTT are air inlet uesin which the dampers DD are fitted. UU are the air outlet flues in which the dampers OO- are fitted'. V is the central air passage. WW are the side air passages between the piles of lumber and .the side walls of the kiln. XXare the main air dis'- tributors. YY are the second diffusers. ZZ are the first diffusers. The plenum chambers between the second diffusers and the first diffusers are the vsecondary plenum chambers. aa are the vertical deflecting ducts. Z112 are the fan housings and partitions. cc and dal are the plenum chamber partitibns. While the drawings show and the specification describes certain specific arrangement of the fans and shaft, this invention is not limited to this particu lar arrangement, since it is obvious that its functions can be performed in an equivalent manner with other arrangements of the fans.

The operation of the kiln is briefiy as fol-v lows: The lumber is placed in the kiln, the doors and all of the dampers are closed, and the kiln is started. Steam is turned into the coils and the steam jets are turned on. Suitable regulating devices are provided to control and regulate the supply of steam to the heating coils and the supply of the steam to the steam jets. If it is found impossible to reduce the humidity to the desired point with the steam jets all turned off', the dampers DD and OO are opened to allow fresh air to enter. and moist air to escape. These dampers should be adjusted so that a humidity below that desired will be secured. The steam jets may then supply a sufficient amount of steam to bring the humidity up to the desired point. Assuming that the direction of rotation of the fans is such that the air and vapor move upward through the lumber piles LL they will pass downward through the central air passage V, throughv the vertical deflectingducts tada, through the fans BB past the side defiecting partitions AA, over the heating coils EE through the two sets of difusers ZZ and YY, and then upward through the lumber piles LL. Vhen the direction of rotation of the fans is reversed the direction of the circulation of-air and vapor is likewise reversed. When the direction of the circulation of the air and vapor is upward through the lumber the various chambers between the fans and the first diffusers and between the first diffnsers and the second diffusers, respectively, are under slight -pressure and act. as plenum chambers. The velocity of the air 'movement through these chambers is comparatively slow. The use of these plenum chambers and the various sets of diffusers in the manner indicated produces a very uniform flow of air through the length of the kiln. The unbalancing effect of the horizontal air flow produced by the fans is practicall)Y elimi* natedby allowing a slight pressurev to build up in the main air distributors. This is still further eliminated by the slight plenumv in the space between the upper and lower distributors. It is obvious that the kilnv would work reasonably well with single sets of difusers for each main air distributor and that stifurther uniformity in airdistribution might be secured by adding a 'third or even a fourth set of diusers. The principle, of course, remains the same and practical expediency will determine the balance between increased uniformity of air distribution secured by theaddition of more sets of distributors and the loss in efficiency which they cause. It. is also obvious that any wellknown form of distributor may be used. The invention is not restricted to the form illustrated in which the openings consist simply of spaces between the slats running the full length of the kiln. The air flow in the present invention differs materially from that in a single track edge stacked kiln because it is necessary to produce two separate and distinct air currents, one for each side of the kiln. To accomplish this it is necessary to provide two sets of diffusers and two sets of plenum chambers, and to locate them at the sides of the fan instead of directly above it. It is necessary also to modify the'air distributing system b'y adding the vertical deflecting ducts. These ducts serve to eliminate longitudinal air movement when the direction of the circulation is upward through the central passage V.

Vhen the direction of the circulation of the air and va or is such that they ass through the di users and plenum cham ers immediately after leaving the lumber piles instead of immediately before entering them,

the air distributing system, which lconsists of the main air distributor, the side,de{iecting partitions, the plenum chambers and the various diffnsers, does not materially assist in g producing a uniform circulation. The com- 4() parativelyrgreat length of travel from the fans to the point at which the air and vapor enter the lumber has been found suicient to produce the desired uniformity in connection with the other features of the design.

' .with manometers and similar instrumentsin the circulation.

The arrangement of the heating coils may be made to assist in smoothing out unevennesses It has been found through experience with a` great manydifferent types of forced circulation in dry kilns that it is not possible to secure uniformity of distribution of the air and vapor if they be handled at high velocities. -In order to produce uniform satisfactory circulation, it is essential that the air and vapor be moved at low velocities and that special means be provided for the uniform distribution of the air and vapor through the kiln. The use of internal fans and large plenum chambers produces this result, since the 'velocity of the air and vapor through the fans themselves is comparatively low and the velocity in the plenum chambers is so small that the velocity head can not be measured Iusually used for the purpose;

' It is well-understood that when the circulation ofthe air and the vaporin the kiln is continuously in one direction, that portion of the pile at whichthe air enters will dry 1 every two or three days or oftener, the exact period being determined by the condition of the lumber in the kiln.

Several arrangements of the plenum chambers are possible and practicable. The principal ob]ect of the plenum chambers and dilfusers is to produce a uniform How of air and vapor through the lumber to be dried, and any detailed arrangement which` will accomplish this result will be satisfactory if at the same time it does not consume an excessive amount of power.

Having fully described the principles of this invention and the manner in which they can be embodied in a dry kiln, I claim as original:

1. In a double track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fans are mounted for rotation.; means for rotating said shaft in either direction to cause reversal of the circulation of the air .and vapor in said kiln; and an air distributing system comprising side deflecting partitions, a mai-n air distributor, vertical deflecting ducts, and two sets of diifusers.

2. In 4a double track dry kiln arranged for edge stacking: a series of fans; a. shaft on which thefans are mounted for rotation; ymeans for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet lnes; and an air distributing system comprising side deliectin partitions, a main air distributor, vertical deflecting ducts, and two sets of diffusers.

- 3. In a double track dry kiln arranged for l l means for heating the kiln and its contents;

and an airdistributing system comprising side ,deflectlng partitions, a main a1r d1stributor, vertical deflecting ducts, and two sets of diifusers.

4. 1In a double track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fans are mounted for rotation air distributor, vertical deflecting ducts, andV two sets of diffusers.

5. In a double track dry Vkiln karranged .for edge stacking: a seriesl of fans; a shaft on Which thefans are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; a vplenum chamber for'y each fan; and a diffuser with restricted discharge passages for each plenum chamber.

6. In a double track dry kiln arranged vfor edge stacking: a series offans; a shaft on which the fans are mounted for rotation; means for rotating said shaftin either direction to. cause reversal of the circulation o-f the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

7 In a d-ouble track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fans are mounted for rotation; meansfor rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air out-- let iues; means for heating the kiln and its contents; a plenum chamber for each fan; and a diffuser with restricted discharge passages foreach plenum chamber.

8. In a double track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fans are mounted for rotation;

- v means for rotating said shaft in either direction to cause reversal of the circulation of the airand Vapor in said kiln ;v dampered air inletl ilues and dampered air outlet iues; means for heating the kiln and its contents; meansfor huinidifying the atmosphere in the kiln; a plenum chamber for each fan;

passages for each plenum chamber.

9. In a double track dry kiln arranged for and a dill'user with restricted discharge edge stacking: a series of fans; a shaft on tion to cause reversal the circulation of the air and vapor in said kiln; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

10. In a double track drykiln arranged for edge stacking: a series of fans; a shaft on which the fans are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and'vap'or in said kiln; dampered air inlet lues and dampered air outlet flues;

a series of plenum chambers for eacln fan;

and a diffuser with restricted discharge passages for each plenum chamber. 11. In a double track dry kiln arranged for edge stacking: aseries of fans; a shaft on Whichthe fans are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet llues and dampered air outlet iues;

direction to cause reversal ofthe circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; a series of plenum chambersfo-r each fan; and a diffuser with restricted discharge passages for each plenum chamber.

13. In a double track dry kiln arranged `for edge stacking: a series of internal. fans;

a, plenum chamber for each fan; and a-dif fuser with restricted discharge passages for each plenum chamber. n

14. In 'a double track dry kiln arranged for edge stacking: a series of internal fans; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber. v y v15. The herein described improvement in the art of drying lumber in a double track dry kiln arranged fori edge stacking; Whih improvement consists in vsubjecting said lumber to a reversible circulation of air and vapor, said air and vapor passing in a substantially vertical direction through the lumber piles. 4

which the yfans are mounted for, rotation; l

means for rotating said shaftin either direc- ROLF THEL. LI. 

